So-called Portland Cement Clinker consists essentially of alite (C.sub.3 S) and belite (C.sub.2 S), tricalcium aluminate (C.sub.3 A) and tetracalcium aluminate ferrite (C.sub.4 AF). Further constituents are in particular free magnesium oxide as well as alkalis.
The cooling of the cement clinker influences its structure, the mineralogical composition and the properties of the cement produced therefrom. The rate of cooling of the clinker has an influence in particular on the ratio between the crystalline phase content and the glass phase content in the clinker. With slow cooling, crystal formation takes place for almost all clinker components, whilst rapid cooling impedes the crystal formation and allows the liquid phase (2,95 Al.sub.2 O.sub.3 +2,2 Fe.sub.2 +MgO+alkalis) to solidify in glass form. The proportion of liquid phase in clinkers from rotary kilns is approximately 20 to 28%.
The rapid cooling of the clinker increases in particular the sulphate resistance of the cement to sulphates (magnesium, sodium, potassium, etc.) Free alkali and MgO cristals (periclase) entering in the glass formation. This may be explained by the fact that the C.sub.3 A content which is responsible of the capacity of cement to sulfates resistance, becomes part of the glass and also free alkali and MgO (periclase), due to rapid cooling of the clinker and therefore will be resistant to attack by sulfates. As free alkalis disappear, free alkalis will not anymore attack the silica in aggregates.
A cement clinker which essentially consists only of alite, belite and glass, i.e. in which C.sub.3 A and C.sub.4 AF are bonded in the glass, could be designated as Glass Portland Cement. It is distinguished in particular by a special capacity for resistance to environmental influences without restriction of its strength.
Although the so-called Glass Portland Cement has already been produced in the laboratory, no method has hitherto been known which permits commercial production thereof.
The necessary rate of cooling cannot be achieved with the clinker cooling processes which are known in the art, particularly with the aid of so-called grate coolers.
A method of producing active belite cement is known from DD-A-206 422. In this case the belite clinker from the rotary kiln is delivered to a first cooling stage into which brown coal dust and low-temperature exit gas contains in particular carbon dioxide and steam. This leads to gasification of the supplied fuel with steam or with carbon dioxide, these gasification reactions extracting the necessary reaction enthalpy from the cement clinker.
The object of the invention is to provide a method and apparatus for industrial production of Glass Portland Cement.